I never quite understood why speed was so intriguing in baseball. Perhaps it is because it is an entirely different skill set than hitting. Maybe it is because it stands opposite of power hitting. It does not require the bat, it is often found in players who lack a good deal of power, and it affects games in a different fashion (though it still contributes to the overall goal of run scoring).
Regardless of why it is so romanticized, baseball fans and people in the business are enamored with speed to some degree. And there is no other event more commonly associated with speed than the stolen base. But for as big a deal as people make about the running game in terms of stolen bases, the topic is rarely discussed in terms of runs or wins. Sure, stealing second gets a runner into scoring position, but how much of an impact does that move have on run scoring? Let’s turn to our old friend, linear weights, for the answer.
With no outs and a runner on first in a five run/game environment, the average team is expected to score 0.950 runs. Moving the runner to second base on a steal yields a run expectancy of 1.192 runs, meaning that the change in run expectancy from that steal was 0.242 runs. The same move with two outs, a move often lauded because the runner is placed in scoring position for the current batter, only yields 0.09 runs on average. In total, in this run-scoring environment, the average stolen base was worth 0.175 runs. A worthwhile move if successful, but hardly worth making a fuss about teams emphasizing.
Furthermore, consider the potential loss in attempting to take bases. Caught stealings cover both pickoffs and normal foiled stolen base attempts. In any of these cases, the loss of a baserunner and the addition of an out far outweigh the gain of an extra base; as a result, in order to break even with the threat of the out, runners have to be more successful on stolen base attempts. The average CS in this run environment was worth -0.467 runs. That means that a baserunner would need a 72.7% success rate in stolen bases in order to break even in run production. In the environments seen between 2007 and 2009, that breakeven rate is a bit lower, at 68.3%. The general rule of thumb used is a break-even percentage of 70%.
Do the players know?
The good news is that it seems like players, managers and the people who send baserunners running that breakeven points are very high. Among all players from 2007 to 2009, no player who has stolen more than 50 bases has a SB% less than 70%. Clearly, players who are good enough to steal 50 bases in three years know what they are doing on the basepaths. In order to find some inefficiency on the bases, I searched for players with large numbers of CS totals. Players who had been caught stealing more than 30 times in those three seasons all had SB% over 70%. When the criterion was brought down to players with at least 20 CS, only three players had a SB% under 70%: Felipe Lopez, Troy Tulowitzki, and David DeJesus.
The stolen base threat at the top
In The Book: Playing the Percentages in Baseball, the chapter involving lineup optimization discusses various aspects of lineup building that can maximize run production. One of the biggest railings against conventional wisdom in that chapter is the use of a stolen base threat. In The Book, it is stated that stolen base threats are not optimally used at the top of the lineup. When considered further, the reasoning seems obvious: the “heart of the order” should contain the team’s best power threats and hitters, the types of hitters who do not need assistance in moving baserunners over. Base stealing threats are best utilized in front of lesser hitters at the bottom of the order. These hitters need help advancing runners, so any bases stolen will add more runs than usually expected from the bottom of the order. Putting runners who are base stealing threats at the top wastes their talents*.
*Note that The Book mentions that runners at the top of the lineup should be fast because of the preponderance of double play opportunities at the top of the lineup. Steals, however, are best used closer to the bottom.
There is certainly value in the stolen base. Any time runners move forward, it is generally a good thing. However, the emphasis on team speed and the need for base stealing speed at the top of the lineup is ofter overplayed to the public. Simply converting these stolen bases into run totals gives a better context to the difference between successful thiefs like Carl Crawford and players like Tulowitzki who have hurt their teams by running.